The Southern Amazon forests, where the Seasonal Perennial Forest occurs, has great influence on the maintenance of the regional physical equilibrium and they are among forests most threatened by anthropic action and are little known in relation to their structure. In this context, the objective of this work was to study phytosociological structure of a Seasonal Perennial Forest area in the Rio das Pacas Basin at Querência, state of Mato Grosso, Brazil. The vegetation sampling was composed of the distribution of 200 center quarter points, all individuals with DAP (diameter to height breast) equal or superior to 10 cm were considered. The total density of the sampled area was 736 ind./ha distributed into 58 species, 45 genera and 31 families. The species of highest Importance Value (IV), Ocotea leucoxylon (Sw.) Laness., Trattinickia glaziovii Swart, Ouratea discophora Ducke, Xylopia amazonica R.E. Fr. and Myrcia multiflora (Lam.) DC. corresponded to 28.45% of the total IV and occurred in other Seasonal Perennial Forest areas in Gaucha do Norte, state of Mato Grosso; however, not with the same representativity. The Shannon index (3.51) may be considered as low in relation to the Amazon Forest; however, the Pielou equability (0.86) suggests that this arborous community presents high floristic heterogeneity. mudanças morfológicas nas raízes relacionadas ao metabolismo secundário, constituindo-sistema-modelo para o estudo da genética, da fisiologia e dos processos morfogenéticos envolvidos na formação de ectomicorriza entre Pisolithus e Eucalyptus.